Efficient Networks Siemens Sinamics S120 - Manual (Page 125)

Vector control
4.5 Speed controller pre-control and reference model
Drive Functions
Function Manual, (FH1), 07/2007 Edition, 6SL3097-2AB00-0BP4
125
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Figure 4-8 Speed controller with pre-control
If the speed controller has been correctly adjusted, it only has to compensate for disturbance
variables in its own control loop, which can be achieved by means of a relatively small
change to the correcting variables. Speed setpoint changes, on the other hand, are carried
out without involving the speed controller and are, therefore, performed more quickly.
The effect of the pre-control variable can be adapted according to the application via the
evaluation factor p1496. If p1496 = 100 %, pre-control is calculated in accordance with the
motor and load moment of inertia (p0341, p0342). A balancing filter is used automatically to
prevent the speed controller from acting against the injected torque setpoint. The time
constant of the balancing filter corresponds to the equivalent delay time of the speed control
loop. Speed controller pre-control is correctly set (p1496 = 100%, calibration via p0342)
when the I component of the speed controller (r1482) does not change during a ramp-up or
ramp-down in the range n > 20% x p0310. Thus, the pre-control allows a new speed setpoint
to be approached without overshoot (prerequisite: the torque limiting does not act and the
moment of inertia remains constant).
If the speed controller is pre-controlled through injection, the speed setpoint (r0062) is
delayed with the same smoothing time (p1442 or p1452) as the actual value (r1445). This
ensures that no target/actual difference (r0064) occurs at the controller input during
acceleration, which would be attributable solely to the signal propagation time.
When speed pre-control is activated, the speed setpoint must be specified continuously or
without a higher interference level (avoids sudden torque changes). An appropriate signal
can be generated by smoothing the speed setpoint or activating the ramp function generator
rounding p1130 – p1131.
The starting time r0345 (T
start
) is a measure for the total moment of inertia J of the machine
and describes the time during which the unloaded drive can be accelerated with the rated
motor torque r0333 (M
mot,rated
) from standstill to the rated motor speed p0311 (n
mot,rated
).
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If these basic conditions are in line with the application, the starting time can be used as the
lowest value for the ramp-up or ramp-down time.